1. Field
The present invention relates to insulating pads for waterbeds and particularly to an insulating pad for an unheated waterbed bladder.
2. Prior Art
It is well known, as indicated in U.S. Pat. No. 4,549,323 to Brockhaus that unheated conventional waterbeds are very uncomfortable for sleeping purposes. In fact, at room temperatures of about 65 to 75 degrees the difference between the body's normal temperature of about 98 degrees and water in the large waterbed bladder will preclude a restful night's sleep. Because of this fact, it is common practice for many owners of waterbeds to leave the bladder heater on twenty-four hours per day.
An evolution which has occurred to overcome the problem associated with great weight and the large volume of cool water present in conventional waterbed bladders is the development of the hybrid waterbed mattresses. A hybrid waterbed mattress is illustrated in U.S. Pat. No. 4,186,455 to Fox et al. and in many of the patents recited in that patent.
A hybrid waterbed mattress generally has a bladder of about four to six inches in depth and has less width and length than a conventional waterbed bladder, resulting in much less water being present in the hybrid mattresses. In a hybrid waterbed mattress there is generally no heater and the person sleeping on the hybrid waterbed mattress is insulated by a foam pad and a conventional quilted cover having a small quantity of cotton or fiberfill material therein. Because of the smaller amount of water present, e.g. about 40% as much as in a conventional waterbed, and the presence of an insulating foam pad, it is possible that the amount of heat escaping a person sleeping upon the hybrid waterbed mattress can warm the water sufficiently so that a comfortable night's sleep might be obtained. Also, because of the insulating foam pad over the hybrid waterbed mattress, there is not a significant amount of heat transferred from the sleeper to the water. A typical cover for hybrid mattresses is illustrated in U.S. Pat. No. 4,316,423 of Nordstrom.
Other attempts to solve the problem with the respect to large conventional waterbed bladders are recited U.S. Pat. No. 4,549,323.
The insulating pad described as the invention of U.S. Pat. No. 4,549,323 is very complex in nature and comprises a number of layers to provide an insulating coverlet for use with a conventional waterbed bladder. While the insulating cover of the 4,549,323 patent may be effective, it comprises a great number of layers of relatively sophisticated materials. Some of the layers are a plastic sheet material containing air pockets or bubbles, which are deemed to be susceptible to wear, resulting in the bubbles being popped and that layer losing its insulating qualities. Furthermore, it is generally not comfortable to sleep upon a plastic sheet material.
Very thick foam pads have been utilized to provide a measure of insulation on the top surface of a hybrid waterbed. A construction is shown in U.S. Pat. No. 4,221,013 wherein two foam layers are used to provide insulation above a plurality of small tubular bladders having a total water content which is only a small fraction of that of a conventional waterbed bladder. Foam, however, tends to compress significantly under load. Also, foam even under a fabric ticking has a feel which many find unacceptable. A foam layer over a water bladder is also illustrated in the hybrid waterbed disclosed in U.S. Pat. No. 4,187,566 of Peterson.
Hybrid waterbed mattresses have become popular because a heater is generally not required and the mattress has the size and appearance of a regular innerspring mattress, as well as greatly reduced weight. The modest amount of insulation required to insulate a sleeper from the smaller volume of water present generally precludes the necessity of a heater. Thus, foam insulation of a few inches in thickness has generally been satisfactory for hybrid waterbed mattresses.
Further efforts to construct a useful insulating coverlet for a conventional waterbed mattress have included a combination of carpet backing, that is, spongy carpet pad material with an overlay of flexible polyurethane foam or a thin layer of conventional Dacron fiberfill material quilted to the carpet backing. While such constructions are relatively inexpensive to make and can be made from readily available materials, such a coverlet is stiff and generally ineffective, and is relatively heavy, hard and very difficult to quilt.